To correlate oxygen consumption, blood flow and Hgb saturation with NADH fluorescence changes in the cat cortex during direct cortical stimulation. If the NADH fluorescence changes can be correlated with separate on line measures of 02 consumption this will strengthen and clarify the relationship between fluorometric changes and 02 consumption rates. In addition, with (K ion) sub 0 and NADH monitoring along with flow some information on the local regulation of cerebral blood flow may be obtained.